Discussion

In this pilot study, we examined the differences between and within a group of patients with CTS and a group of age and gender matched controls after completing a texting task. This study found that patients with CTS experienced more symptoms and had more impairment to sensation compared to age and gender matched controls at all time points. In terms of texting performance, patients also performed worse than controls.

Study Feasibility:

This pilot study can be expanded into a full study with some changes to the exclusion criteria. Our primary focus for this study was to examine the feasibility of recruiting patients for this study. We were able to determine a sample size that was under 300 subjects, have an exclusion criteria rate less than 60%, participation rate greater than 20%, and have a withdrawal rate of less than 20%. Recruitment of patient participants by surgeons seems to be the most optimal method, as most patients were willing to participate. Our exclusion criteria for excluding any potential patient with other recent hand injuries were too conservative at times. We felt that hand injuries occur commonly and we were limiting our recruitment to patients with CTS and no other

injuries. For example, a patient who has a minor bruise or cut on the palms could be recruited. In addition, diabetics who are not insulin dependent could be included in this study. Those with diabetes were originally excluded from this study was because they were assumed to all suffer from neuropathy and have altered sensation caused by diabetes. However, not all diabetics suffer from peripheral neuropathy 39 and patients with diabetes without neuropathy could be recruited for the study. These considerations may help increase the recruitment of patient participants by changing the exclusion criteria to be more liberal. The age range was

appropriate, as we captured the age range of working adults and the ages when most patients suffer from CTS. Aging has been associated to age related changes to sensory threshold 34, 3536-

38

Recruiting controls was not an issue for this pilot study, as many healthy hospital workers were available for the study, and were willing to participate. Candidates who would qualify for the control group would be considered anyone without CTS and any other injury to the upper extremity. A total of 20 controls were recruited for the study, but only 15 controls were

analyzed. During the recruitment process of healthy controls, no records were made to document how many hospital staff were asked to participate in the study. Controls were invited to be part of the study by word of mouth and announcements made at the staff meetings at the hand therapy and physiotherapy department of the tertiary center. Nineteen controls were recruited by word of mouth and would probably be the best way to approach controls for a larger study. As for

posters posted in the hospital hallways, only one control was recruited. Overall, the best strategy for recruiting controls seems to be by word of mouth and announcements.

As hypothesized, patients experienced more classical symptoms of CTS compared to controls at baseline in this study. However, pain and numbness were not significantly different after texting for the patient group, but scores did increase gradually during texting and decreased after texting. Pain and numbness may have increased from wrist posture, combined with

constant gliding of the tendons in the carpal tunnel with repetitive forces, which could increase the pressure exerted against the median nerve, and associated structures, aggravating symptoms. Kier et al 9 did a biomechanical study examining the changes in carpal tunnel pressure from changes in wrist posture (extension versus flexion and radial versus ulnar deviation) and with finger posture (0, 45, or 90 degrees flexion). The study found that carpal tunnel pressure increased the most with wrist extension with straight fingers. Radial and ulnar deviations also increased carpal tunnel pressures. 9 This study suggested that the increased pressure could aggravate symptoms in patients with CTS based on hand postures. 9In addition, since the texting activity required force application on the distal pulp of the thumbs, it is possible the force could also aggravate the symptoms during texting. Rempel et al 40 performed a biomechanical study, and found that the application of a force at the tip of the digits increased carpal tunnel pressure. In our study, posture and forces at the pulps of the thumbs were not measured, but could be performed in future studies to track changes to these variables throughout texting. Most patients in our study needed to shake their injured hand(s), or have the forearm point downwards with the wrist in neutral position to minimize the numbness the patient participants were experiencing

after texting. The neutral wrist posture and having the forearm pointing downwards may have helped to alleviate symptoms by decreasing carpal tunnel pressure.

However, it is important to note that the gradual increase in pain and numbness lacked potential power to conclude results on the effects of cell phone texting within groups. The small sample size of 15 participants is not large enough to say this did not happen by chance. The sample size calculation for each measurement outcome demonstrated that the sample size of 15 participants per group was too small (Table 4). A future study should be performed to determine the sample size required for more conclusive results for within group comparisons.

Patients also demonstrated a significant increase in touch threshold after texting, and also at 5 and 10 minutes after texting (Figure 2). It has been established in previous literature that patients with CTS have higher touch threshold levels than healthy individuals.10, 11 Compression of the median nerve may decrease the nerve conduction velocity and magnitude of signals from the Merkel disks and Pacinian corpuscles, resulting in a higher touch threshold in the thumbs. Thus, more pressure was required for patients to detect touch stimuli. In a study by Gelberman et al, 41 the researchers tested the influence of different carpal tunnel pressures on touch

threshold, nerve conduction tests, and functional tests in 12 healthy individuals. The participants had their carpal tunnel pressure increased with a catheter, and outcome measures were taken at baseline and after carpal tunnel pressure were increased. 41 They found that as carpal tunnel pressure increased, touch threshold values with the Semmes Weinstein monofilament also increase. 41 There was an increase in self-reported parathesia with increased carpal tunnel pressure. 41 This may suggest that texting on a cell phone increases carpal tunnel pressures for patients with CTS, and results in increased touch threshold values. Even after the testing, PSSD scores for patients did not return back to levels at baseline for patients. However, the PSSD may have high measurement error, as the confidence intervals are fairly wide. The PSSD might be a very sensitive tool for detecting abnormal sensation, as it has high sensitivity for detecting diseases, such as neuropathies caused by diabetes, 42 and CTS. 43 Its sensitive nature might be demonstrated in its ability to measure change after texting activity.

Both controls and patients experienced fatigue after texting. A study that supports our findings on fatigue examined the occurrence of muscle fatigue in the forearms of computer users after prolonged typing. Lin et al 44 used electromyography to quantify forearm muscles in 30 female typists who typed for 2 hours continuously. They found that 74% of the measured forearm muscles manifested fatigue, and that extensor digitorum communis presented more fatigue than forearm flexor muscles. 44 The sensation of fatigue may have resulted from lactic acid accumulation in the thenar and forearm muscles, as a result of contraction of muscles in the hand during texting activity. Fatigue was present in the computer typing tasks requiring long term dynamic contractions with forces less than 10% of maximum voluntary contractions. 44 Future research should be done to verify the mechanisms behind fatigue in low level hand activity and in patient populations requiring cell phone texting as part of their daily activity.

Red blood cell concentration values from the TIVI remained relatively stable throughout the study for both patients and controls. Patients had higher red blood cell concentration than the controls throughout the study. This finding is similar to results a study by Gelberman et al, 41 where arterial and venous blood flow did not change by increases in carpal tunnel pressure among healthy individuals. 41 Previous studies have found that patients with CTS have slower blood flow compared to controls. 45, 46 The differences in findings in our study and previous studies may be due to the penetration ability of the light used in quantifying blood flow between different methods of examining blood flow. Other studies had used Laser Doppler Systems, which examines deep into tissue and provide a more precise measurement of blood flow. The TIVI software only measures red blood cell concentration on the superficial skin level, so deeper blood flow was not measured. This study is one of the initial studies on measuring superficial blood flow in patients with CTS. We suggest there should be more studies on this topic in the future.

As expected, patients typed fewer characters and had slower texting speed. Patients may have performed worse than controls because the texting activity may have aggravated their symptoms, so the patients texted fewer characters and texted slower to reduce the symptoms. We had 3 patients who stopped texting early before the 15 minute mark because the numbness was

Guftasson et al, where young adults were asked to text on a cell phone and had

electromyography and performance measurements (i.e. texting duration) taken. 5 In a subgroup analysis of the group with hand/arm symptoms, they required less time to perform the texting task compared to individuals without symptoms. 5 Despite this difference, our study had a specific patient population which was clinically diagnosed and did not have comorbidities.

This study has a number of strengths and novel findings. It evaluated patients and controls using self-reported measures which would accurately measure their symptoms which they feel and how these symptoms changed over time. The tools used in this study are commonly used within clinical and ergonomic settings and these tools would be highly accessible. This study also compared patients with CTS to an age and gender matched control group. Our study had patients between the age ranges of 29 to 65 years of age. Women between 35 to 44 years of age have the highest rates of CTS claims from work, and for men between ages 35 to 54 years of age in Canada. 47 Previous studies examining texting have primarily focused on younger adults in university settings, 6, 4849 , but did not report the ages of the participants. Additionally,

university students would not accurately represent the general working adult population between 35 to 65 years old. The texting activity was designed to simulate an environment outside of a laboratory. The task allowed participants to choose a posture that was comfortable to them, to accommodate for variability in hand, and trunk postures while in seated position. The

questionnaire used for the texting intervention also contained open ended questions, which allowed for variability in responses according to the participants’ preferences.

Our study also had some potential weaknesses. We recruited a small sample size of patient participants and controls. A larger sample of patient participants would be required to have sufficient power in multivariate calculations, and decrease the probability of potential type II error to allow for more conclusive results on between and within group differences. In addition, we used only one model of cell phone for our study. The nature of the texting activity in this study was restricted to texting with only the thumbs. Performance may vary depending on the specific digits used for texting and on the model of cell phone used for texting. We recommend future studies to use different models of cell phones.

3.10

This pilot study provides valuable information on how cell phone texting affect patients with CTS. The study found that patients experienced more symptoms than controls after texting. Patients with CTS also performed worse than age and gender controls in texting. However, the results were under powered to make conclusive statements. This pilot study also provides important information for future studies involving patients with CTS and cell phone texting.

3.11

1. CTIA (International Association for the Wireless Telecommunications Industry). CTIA (International Association for the Wireless Telecommunications Industry). Available at: http://www.ctia.org/consumer_info/service/index.cfm/AID/10323. Accessed June/20, 2012.

2. Williams IW, Kennedy BS. Texting tendinitis in a teenager. J Fam Pract. 2011;60:66- 7, 1 p following 67.

3. Ashurst JV, Turco DA, Lieb BE. Tenosynovitis caused by texting: an emerging disease. J Am Osteopath Assoc. 2010;110:294-296.

4. Ming Z, Pietikainen S, Hänninen O. Excessive texting in pathophysiology of first carpometacarpal joint arthritis. Pathophysiology. 2006;13:269-270.

5. Gustafsson E, Johnson PW, Hagberg M. Thumb postures and physical loads during mobile phone use - A comparison of young adults with and without musculoskeletal symptoms. Journal of Electromyography and Kinesiology. 2010;20:127-135. 6. Lin I-, Peper E. Psychophysiological patterns during cell phone text messaging: A preliminary study. Applied Psychophysiology Biofeedback. 2009;34:53-57.

7. Werner RA, Andary M. Carpal tunnel syndrome: pathophysiology and clinical neurophysiology. Clinical Neurophysiology. 2002;113:1373-1381.

8. Kerwin G, Williams CS, Seiler 3rd J. The pathophysiology of carpal tunnel syndrome.

9. Keir PJ, Bach JM, Rempel DM. Effects of finger posture on carpal tunnel pressure during wrist motion. J Hand Surg. 1998;23:1004-1009.

10. Gelberman RH, Hergenroeder PT, Hargens AR, Lundborg GN, Akeson WH. The carpal tunnel syndrome. A study of carpal canal pressures. J Bone Joint Surg Am. 1981;63:380-383.

11. Rojviroj S, Sirichativapee W, Kowsuwon W, Wongwiwattananon J, Tamnanthong N, Jeeravipoolvarn P. Pressures in the carpal tunnel. A comparison between patients with carpal tunnel syndrome and normal subjects. Journal of Bone and Joint Surgery - Series B. 1990;72:516-518.

12. Phalen GS. The Carpal-Tunnel Syndrome: SEVENTEEN YEARS'EXPERIENCE IN DIAGNOSIS AND TREATMENT OF SIX HUNDRED FIFTY-FOUR HANDS. The Journal of Bone and Joint Surgery. 1966;48:211.

13. Werner R, Armstrong TJ, Bir C, Aylard MK. Intracarpal canal pressures: The role of finger, hand, wrist and forearm position. Clin Biomech. 1997;12:44-51.

14. O'Doherty J, Henricson J, Anderson C, Leahy MJ, Nilsson GE, Sjoberg F. Sub- epidermal imaging using polarized light spectroscopy for assessment of skin microcirculation. Skin Res Technol. 2007;13:472-484.

15. McNamara PM, O'Doherty J, O'Connell ML, et al. Tissue viability (TiVi) imaging: temporal effects of local occlusion studies in the volar forearm. J Biophotonics.

16. Henricson J, Nilsson A, Tesselaar E, Nilsson G, Sjoberg F. Tissue viability imaging: microvascular response to vasoactive drugs induced by iontophoresis. Microvasc Res. 2009;78:199-205.

17. Nilsson GE, Zhai H, Chan HP, Farahmand S, Maibach HI. Cutaneous bioengineering instrumentation standardization: the Tissue Viability Imager. Skin Res Technol.

2009;15:6-13.

18. Dellon AL, Keller KM. Computer-assisted quantitative sensorimotor testing in patients with carpal and cubital tunnel syndromes. Ann Plast Surg. 1997;38:493. 19. Jensen MP, Gammaitoni AR, Olaleye DO, Oleka N, Nalamachu SR, Galer BS. The Pain Quality Assessment Scale: Assessment of Pain Quality in Carpal Tunnel Syndrome.

Journal of Pain. 2006;7:823-832.

20. Victor TW, Jensen MP, Gammaitoni AR, Gould EM, White RE, Galer BS. The dimensions of pain quality: factor analysis of the Pain Quality Assessment Scale. Clin J Pain. 2008;24:550-555.

21. Waterman C, Victor TW, Jensen MP, Gould EM, Gammaitoni AR, Galer BS. The Assessment of Pain Quality: An Item Response Theory Analysis. Journal of Pain. 2010;11:273-279.

22. Strauch B, Lang A, Ferder M, Keyes-Ford M, Freeman K, Newstein D. The ten test.

23. Yamagishi A, Morita T, Miyashita M, Kimura F. Symptom prevalence and

longitudinal follow-up in cancer outpatients receiving chemotherapy. J Pain Symptom Manage. 2009;37:823-830.

24. Levine DW, Simmons BP, Koris M, et al. A self-administered questionnaire for the assessment of severity of symptoms and functional status in carpal tunnel syndrome.

JOURNAL OF BONE AND JOINT SURGERY-AMERICAN VOLUME-. 1993;75:1585- 1585.

25. Greenslade JR, Mehta RL, Belward P, Warwick DJ. Dash and boston questionnaire assessment of carpal tunnel syndrome outcome: What is the responsiveness of an outcome questionnaire? J Hand Surg. 2004;29 B:159-164.

26. Katz JN, Gelberman RH, Wright EA, Lew RA, Liang MH. Responsiveness of self- reported and objective measures of disease severity in carpal tunnel syndrome. Med Care. 1994;32:1127-1133.

27. Chatterjee JS, Price PE. Comparative responsiveness of the Michigan Hand

Outcomes Questionnaire and the Carpal Tunnel Questionnaire after carpal tunnel release.

J Hand Surg Am. 2009;34:273-280.

28. Brant R. Inference for Means: Comparing Two Independent Samples Available at: http://stat.ubc.ca/~rollin/stats/ssize/n2.html. Accessed 10/30, 2012.

29. Goldsmith CH, Boers M, Bombardier C, Tugwell P. Criteria for clinically important changes in outcomes: Development, scoring and evaluation of rheumatoid arthritis patient and trial profiles. J Rheumatol. 1993;20:561-565.

30. Stern LD. A Visual Approach to SPSS for Windows. 2nd ed. Pearson; 2010. 31. Micceri T. The unicorn, the normal curve, and other improbable creatures. Psychol Bull. 1989;105:156.

32. Gardner RC. Psychological Statistics using SPSS for Windows. Prentice Hall Upper Saddle River, NJ; 2001.

33. Geisser S, Greenhouse SW. An Extension of Box's Results on the Use of the $F$ Distribution in Multivariate Analysis. The Annals of Mathematical Statistics.

1958;29:885-891.

34. Povlsen B. High incidence of absent nerve conduction in older patients with bilateral carpal tunnel syndrome. Ann R Coll Surg Engl. 2010;92:403-405.

35. Blumenthal S, Herskovitz S, Verghese J. Carpal tunnel syndrome in older adults.

Muscle and Nerve. 2006;34:78-83.

36. Bodofsky EB, Campellone JV, Wu KD, Greenberg WM. Age and the severity of carpal tunnel syndrome. Electromyogr Clin Neurophysiol. 2004;44:195-199.

37. Kouyoumdjian JA, Zanetta DMT, Morita MPA. Evaluation of age, body mass index, and wrist index as risk factors for carpal tunnel syndrome severity. Muscle and Nerve. 2002;25:93-97.

38. Kouyoumdjian JA. Carpal tunnel syndrome. Age, nerve conduction severity and duration of symptomatology. Arq Neuropsiquiatr. 1999;57:382-386.

39. Smith AG, Singleton JR. Diabetic neuropathy. CONTINUUM Lifelong Learn Neurol. 2012;18:60-84.

40. Rempel D, Keir PJ, Smutz WP, Hargens A. Effects of static fingertip loading on carpal tunnel pressure. Journal of Orthopaedic Research. 2005;15:422-426.

41. Gelberman RH, Szabo RM, Williamson RV, Dimick MP. Sensibility testing in

peripheral-nerve compression syndromes. An experimental study in humans. The Journal of bone and joint surgery.American volume. 1983;65:632.

42. Carvalho VF, Ferreira MC, Vieira SAT, Ueda T. Cutaneous sensibility threshold in the feet of diabetic patients with pressure specified sensory device: an assessment of the neuropathy. Revista da Associação Médica Brasileira. 2009;55:29-34.

43. Tassler P, Dellon A. Correlation of measurements of pressure perception using the pressure-specified sensory device with electrodiagnostic testing. Journal of occupational and environmental medicine. 1995;37:862.

44. Lin MI, Liang HW, Lin KH, Hwang YH. Electromyographical assessment on

muscular fatigue--an elaboration upon repetitive typing activity. J Electromyogr Kinesiol. 2004;14:661-669.

45. Galea LA, Mercieca A, Sciberras C, Gatt R, Schembri M. Evaluation of sympathetic vasomotor fibres in carpal tunnel syndrome using continuous wave Doppler

46. Yayama T, Kobayashi S, Awara K, et al. Intraneural blood flow analysis during an